Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!

Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.

Just to let you know that the Megasquirt is a good device but for installation on a Subaru to control both Fuel and Spark it it is not easy unless you switch to an EDIS system.

I am currently working on a MS-II installation without EDIS and it requires some code modification to correctly control when fuel is injected (work is in progress and going well).

For spark control there is quite some work to be done since I want to use stock ignition system (wasted spark with a coil and ignitor assembly). The big problem is to know what signal the stock ECU sends to the ignitor + coil assembly, once I know this I think it will be relatively easy to implement.

If you do a search on the Megasquirt forum you will see that most people who have installed it on a Subaru have switched to EDIS. Why did'nt I switch to EDIS ? Well for the fun of it and provide to Subaru owners an easy installation.

I'm looking at the Extra code since it already has code for dual VR and dual spark output. Again, code modification needed but I'm still working on the 2nd VR circuit. The stock ECU only drives another pair of transistors at the ignitor so you only needed a pair of small NPN transistors (from the service manual diagram). At the end of the day, if the code route doesn't work out, the Extra code has a wheel decoder so I can technically put a 60-2 / 36-1 wheel on the crank pulley (much like how people install TEC-II in the early RS-T days) with the associate sensor and still use the stock ignitor instead of EDIS.

I believe it is possible to install the Megasquirt to control fuel and let the ECU take care of the rest. At least that's what I goiing for as a first step with my Megasquirt II.

For controlling spark if anybody has details about the signals sent by the stock ECU of a MY00 2.5RS that would be great. If I am not wrong the "ignitor + coil assembly" has two banks controlled individually, the assembly has a four wires connectors. Are those signals 0/+12V square waves ? 0/+5V ?

At this point nobody had the same setup as you - the guys that had Megasquirt, ran on EA engines and used Ford EDIS and a 36-1 wheel on much older car. Looks like cirecan is working a MS-II installation (custom code), and I'm trying to work on a MSnS-E installation (again, custom code), both using stock trigger on the MY00 (I suspect the MY99 might use the same trigger but it might use the same one as the WRX). The biggest problem is that there is no support for stock hardware - if you can, you might have better luck mating a 36-1 wheel on the pulley ) aligned with a Hall sensor (or 60-2 wheel like the TEC-II). Coolant sensor is another tricky area that I know I will run into.

The MS-II's downside is the single ignition output which requires more hardware (GPIO board) that hasn't been available to the public yet, the MSnS-E lacks the microsecond resolution but it at least has the option to support up to 6 ignition.

Good timing this thread as far as I'm concerned; I've got my MS-II all assembled and I was planning on wiring it in this weekend.

Quote:

I am currently working on a MS-II installation without EDIS and it requires some code modification to correctly control when fuel is injected

Can you give me more information about that? I was planning on doing the same thing; using MS-II for fuel and leaving spark on the stock ECU. What is the problem that needs you to do code changes? I was planning to run the tacho output from the stock RS ECU to MS-II for engine speed, and I thought it doesn't matter what the advance is on that signal since it's only for fueling.

Also, I have absolutely nothing to go on for initial VE table, I was just going to try and figure it out as I go. Can anyone provide anything to start with, or suggestions how I might find something?

For VE table, you might want to look at the dyno graph from SPO and massage those numbers to be at the crank and generate a VE table out of it. I know for fueling you don't need to worry about the stock trigger since you have use the tach output as the trigger for the MegaSquirt - shouldn't need a code change for just that.

There is also some auto VE stuff that could be of help. I dont' know if it's for starting from scratch and building a rough table or dialing in on an already roughed in table, tho... but I think Megatune will at least give you an approximate based on displacement, power output and maybe a few other items...

Hi again,
After thinking about it, and reading comments, it's true that for fuel control only it does not really matter when fuel is injected. Anyhow the MS has only two injector banks so it will always happen that fuel will be injected on closed valves. I am not a mechanic so can this be a source of problem?...if anybody can reassure me on this.

I already tried using the tach output but I kept loosing my stock RPM reading no matter what I tried. I do agree that this is a good solution for fuel control only.

I decided to switch to try decoding the crank signal since anyway I was going to need it eventually. So far the modification I made to decode the stock crank trigger is working, I get a good RPM reading that match the stock tachometer. I need to do more tests but so far so good.

Sequential injection can give a slight edge, both in terms of performance and emission, but to do it properly requires a lot more tuning and support from the hardware. Multi-port Batch injection works well enough that it's not a concern, and injecting fuel on closed valve cools it a little.

cirecan: are you running the MegaSquirt in parallel, sharing the shielded crank signal with the stock ECU? Did you use the cam signal as well to find out which bank to fire? I went with MSnS-E initially because of the feature set and some existing assembly code that roughly resemble what I'm going to do - I think I will have more trouble trying to keep the shielded wiring on the crank and cam signal while sharing the wires among 3 ECUs (stock, Link and MegaSquirt) and trying to verify that my code works

Yes I am running the Megasquirt in parallel. I am sharing the crank signal with the ECU. I am not using the shield, I have taken the signal directly from the ECU connector. I don't have an oscilloscope to verify how clean the signal is but as long as it works

For now I am not using the cam signal since I want the MS to control fuel only as a first step.

For controlling spark I will build a simple circuit that will combine the cam and crank signal to automatically synchronize on #1 cyl. burning phase (#3 cyl compression). I already have 'designed' the circuit, in theory it should work but this is still to be proven. The circuit will output the crank signal but only once it is synchronized on #1 cylinder. This will be of great help because the Megasquirt will always receive the same first crank tooth signal/interrupt.

I did it the other way - feed the cam signal into MegaSquirt, and write code to support it. With a MY00 2.5RS, it's wasted spark and the cam wheel has 3 teeth in between 10* BTDC Cyl 1 and 97* BTDC Cyl 3 which is used as a sync. After that, it's a matter of counting teeth.

Are you only using the cam signal ? I never thought of using only the cam signal. I am not sure how simply the cam signal could be used to distribute spark with some precision. I will need to recheck the timing chart. Thank you for sharing your ideas.

I already tried using the tach output but I kept loosing my stock RPM reading no matter what I tried. I do agree that this is a good solution for fuel control only.

I had the same problem a while ago when I was trying to connect the tach signal to my TechEdge wideband O2 for logging. It's because the signal is a 0-12V signal, and connecting it to a 5V device for logging ends up clamping it through the 5V IC's upper-rail protection diode. I put a resistor (can't remember exactly, about 1K) between the tach signal and the WBO2 and it worked fine.

I got as far as installing just the input signals on the MegaSquirt on the weekend, and I used the same (after the 1K resistor) signal into the MS. I bypassed both the opto-iso and the VR circuits on the MS and just wired it straight into the digital input ("TachSel" I think the jumper point is called). That worked fine, and I'm getting reliable RPM.

No I mean feeding both cam and crank signal into the MegaSquirt for processing instead of extra hardware since the MSnS-E have enough input for it - the MS-II is too tight in terms of input/output but right now I have a different problem to deal with first.

If you're only doing fuel, just make sure the tach signal is converted to 5V and you can wire it directly to the CPU like Aus_RS did since the tach signal is a perfect square wave which is what the CPU expected